Php tutorial, Login script with Jquery

First of all we are goind to make the html form which it is well designed in css3<html>
<head>
<title>Php And Jquery Login tutorial</title>
<link rel="stylesheet" href="style.css" type="text/css">
<script src="jquery-1.8.2.min.js" type="text/javascript"></script>
<script src="code.js" type="text/javascript"></script>
</head>
<body>
<div id="alert">Please type something.</div>
<div id="box">

Here comes the jquery part, i added some validations and a post method handled by php$(document).ready(function(){// hide alert boxes$('#alert').hide();// empty() function used when there is nothing entered
// lets declare the variables for easier usage